Marine Pollution

Litter in the oceans may cause harm to marine wildlife. Seals, birds or other animals may for example
get tangled or mistakenly think it is food, swallow it and starve or suffocate.

Litter is too small to be detected on satellite images. However, there are indirect factors that can be detected by means of remote sensing.
Possible transport pathways of litter may be influenced by ocean currents which in turn can be detected with the use of
satellite imagery.

Photo: Partially sunk New Flame vessel in the Strait of Gibraltar in August 2008. David Parody / Marine Photobank

The waste heat from electrical generating stations is transferred to cooling water obtained from local water bodies such as
a river, lake, or ocean. The water is subsequently returned to the water body with a temperature higher than the ambient
water temperature. A thermal shock to aquatic organisms can be the result.

Water temperatures can be detected with space- or airborne thermal infrared sensors.

The image below shows a thermal plume of cooling water which was made visible by an airborne thermal sensor.
Image Source: Geomatics Group, Environment Agency, UK

Phytoplankton can form harmful algal blooms that can clearly be detected in the
visbile bands of satellite images.

The image below shows a so called Red Tide off the Texas Coast in September 2000.
Image source: NASA

Species of fish brought to new environments (e.g. by tourists) may thrive and outcompete native species.
They can thus be considered to be a form of marine pollution.
This happened for example with the red lionfish, a native to the Indo-Pacific region that is now
present along the East coast of North America.

Invasive marine animals are too small to be detected on satellite images.
However, there are indirect factors that can be detected by means of remote sensing.
The habitat of fish is influenced by water temperature. The latter can be detected with thermal sensors on satellites.
The pathways of fish may be influenced by ocean currents which can in turn be detected with the use of satellite images.

Photo: Chip Baumberger / Marine Photobank

Marine Pollution Quiz:

Which of these do you think are Marine Pollutants?

And which of them can be detected on a satellite image?

Click on an image to find out

Large amounts of sediments can destroy marine habitats such as coral reefs. Transport of sediments from land into the seas
are often indirectly due to human activity. Soil erosion is one consequence of deforestation and of increased
intensity of droughts and rainfall due to climate change.

Image: From the desert areas of Senegal in the north to the vegetated coastal plains of Guinea-Bissau,
The Gambia and southern Senegal (shown in red on the image) - an area which has been subjected to large scale
deforestation. The green colour of the sea around the islands is caused by sediment being swept out to sea from the rivers.

Image source: ESA
Photo: Manfred Morgner / Wikimedia Commons

Atmospheric deposition is marine pollution caused by air pollution. Products of incomplete combustion for example
make up for approximately 13% of the total volume of oil pollution input into the World Ocean (GESAMP 1993). Thus car exhausts are
considered to be a form of marine pollution!

However, the fraction of this oil in the sea water is too scmall to be detectable by means of remote sensing.

Photo: Wikimedia Commons

Chemicals spillt at sea can be toxic to both human and marine life.

If the fraction of chemicals in the water is relatively large (e.g. following a spill), they can be detected
by means of remote sensing for example by using airborne laser sensors.

Radioactive substances in the sea can adversely affect marine wildlife.

They can can however not be detected by means of remote sensing.

Icon: Wikimedia Commons

The Pacific Oyster is a native species of the Pacific coast of Asia. It has become an alien invader
in Europe, New Zealand, Australia and North America. It interacts with local flora and fauna and sometimes takes over
their habitat. In most cases the Pacific Oyster has been brought to other regions intentionally for commercial farming.

It may thus be considered to be a form of marine pollution
(depending on strongly on how ' marine pollution' is defined)

Inavasive species and their habitats such as the reefs that the oyster builds are too small to be detected on satellite images.
They can however be seen on aerial photographs, although you need to be very experienced to find them.
(In this case the oyster reefs are the dark parts within the red circle)